LIFE-CYCLE STRATEGIES AND SEASONAL-VARIATIONS IN DISTRIBUTION AND POPULATION-STRUCTURE OF 4 DOMINANT CALANOID COPEPOD SPECIES IN THE EASTERN WEDDELL SEA, ANTARCTICA

The dominant Antarctic copepod species Calanoides acutus, Calanus prop inquus, Rhincalanus gigas and Metridia gerlachei were investigated wit h respect to their abundance, vertical distribution, developmental sta ge composition, dry weight and lipid content. The specimens were sampl ed during three expeditions to the eastern Weddell Sea in summer (Janu ary/February 1985), late winter/early spring (October/November 1986) a nd autumn (April/May 1992) between 0 and 1000 m depth to follow the se asonal development of the populations. Three species were most abundan t in April, only C.propinquus reached highest concentrations in Februa ry. A seasonal migration pattern was evident in all four species, but was most pronounced in C.acutus. In October/November, they inhabited d eeper water layers, their ascent started by mid-November and in mid-Fe bruary the species concentrated in the upper 50 m, except for M.gerlac hei (50-100 m). Their descent was observed in April/May. The stage com position changed dramatically with season, the older developmental sta ges (CIII-CVI) dominated the populations in late winter/early spring, whereas younger stages (CI and CII) prevailed during summer (C.acutus, C.propinquus) or autumn (R.gigas, M.gerlachei). Only C.acutus ceased feeding in autumn and diapaused at depth. Strong differences between s easons were also detected in dry weight and lipid levels, with minima in late winter/early spring and maxima in summer (C.acutus, R.gigas) o r autumn (C.propinquus, M.gerlachei). Lipid reserves seem to be most i mportant for the older stages of C.acutus and C.propinquus. Based on t hese seasonal data, different life cycle strategies are suggested for the four species.